I've gone back to ask the question, but the more I think about it, the more I'm thinking that this might end up being a red herring as well. I've included below Kimme's exact response:
"in the first edition of "The Official Book of King's Quest" by Donald
B. Trivette, there are SCI code snippets for smoke, opening/closing a
house door, and falling on rocks in the "Script Interpreter" section of
"Chapter 2: The Making of King's Quest 4" (pages 17 to 20).
The 2nd edition doesn't have the codes reprinted. It just has a small
snippet of older AGI coding demonstrating how smoke moves in "Chapter 2:
The Making of Quests" (page 20)."
The reason I am starting to think that it might be a red herring is because I clearly remember that my copy of The Official Book of King's Quest had code in it for "smoke", "falling on rocks", and "opening and closing a house door", i.e. all of the things that Kimme mentions as being SCI code. My copy had AGI code though. Kimme says that the 2nd edition only had AGI code for the smoke but I'm certain my copy had AGI code for the others as well. So unless there is an in between edition (i.e. a first edition with the code changed to AGI instead) then I think it might end up being AGI code that she has seen. I've sent her some examples of AGI and SCI code, highlighting the differences, so that she can verify which it is that she saw. I forget that not all Sierra fans know what AGI and SCI code looks like.